U.S. Pat. No. 6,995,728 B2 describes a horn antenna with a pyramid-shaped horn funnel and a ridge. Said horn antenna comprises a first and a second conducting wall, which walls are disposed so as to form an angle in relation to one another. The horn antenna also has a first ridge in the vicinity of the first conducting wall and a second ridge in the vicinity of the second conducting wall, the first ridge extending over the averted end of the first wall and the second ridge extending over the averted end of the second wall. The curvature of the first ridge corresponds to an arc which is tangent to a line that is perpendicularly upright on the surface of the first wall.
The disadvantage of the horn antenna described in U.S. Pat. No. 6,995,728 B2 lies in the fact that the antenna gain is subject to major fluctuations, particularly at low frequencies. Furthermore, the antenna gain drops to less than 0 dBi at low frequencies, such as frequencies around 1 GHz for example.
A further disadvantage of this horn antenna consists in the fact that the voltage standing wave ratio in the lower frequency range is very unfavorable, with values of between 2 and 5, since it is scarcely possible to operate the horn antenna from a VSWR of about 3.